1. Technical Field
The disclosure relates in general to a semiconductor structure, and more particularly to a semiconductor structure having a stable threshold voltage.
2. Description of the Related Art
In the semiconductor technology, the feature size has been reduced in the recent decades. In the meantime, the rate, the efficiency, the density and the cost per integrated circuit unit have been improved. For semiconductor elements operated under high voltage or ultra-high voltage, such as metal oxide semiconductors (MOSs), issues regarding electrical performance usually arise while MOS transistors with reduced sizes are operated under high voltage.
Therefore, researchers are working on providing stable high voltage (HV) devices.